Downhole tools used for geophysical exploration often include sensors for collecting information about ambient subsurface materials. Sensors may include ones such as those used for resistivity measurements and imaging. The shape and size of a borehole within a geological formation may be valuable information that can provide detail on the integrity of the borehole and the presence of geomechanical problems such as hole damage and wash-outs. The information can also be used to serve as a basis for decision making in the later stages, e.g. for the casing and cementing of a borehole within the geological formation. Moreover, measurements (e.g., resistivity measurements) made by the downhole tool may be sensitive to the shape and size of the borehole, and accurate knowledge of borehole shape/size can serve as a basis for obtaining more accurate measurements. Mechanical and/or acoustic calipers and other devices can be used to measure the distance between the downhole tool and the geological formation. But such devices may not be suitable for use while drilling. Thus, it is desirable that the standoff between the surface of the downhole tool to the wall of a borehole penetrating the geological formation be known so that more accurate measurements regarding the geological formation can be taken, particularly while drilling.